Joining Technology of gamma-TiAl Alloys

179 Pages·2017·5.06 MB·English

by  Sonia Luisa dos Santos Simoes

Joining Technology of
-TiAl Alloys

Joining Technology of
-TiAl Alloys
Sónia Simões
Filomena Viana
Manuel F. Vieira
CEMUC
Faculdade de Engenharia da Universidade do Porto (FEUP)
Universidade do Porto
Porto
Portugal
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A SCIENCE PUBLISHERS BOOK
A SCIENCE PUBLISHERS BOOK
Cover illustrations reproduced with kind permission of the fi rst author of the book, Sónia Simões
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Library of Congress Cataloging-in-Publication Data
Names: Simões, Sónia. | Viana, Filomena. | Vieira, Manuel F.
Title: Joining technology of gamma TiAl alloys / Sónia Simões, Filomena
Viana, Manuel F. Vieira, CEMUC, Faculdade de Engenharia da Univeridade do
Porto (FEUP), Universidade do Porto, Porto, Portugal.
Other titles: Joining technology of gamma titanium-aluminum alloys
Description: Boca Raton, FL : CRC Press, 2017. | “A Science Publishers book.”
| Includes bibliographical references and index.
Identifi ers: LCCN 2017008753| ISBN 9781498738743 (hardback : alk. paper) |
ISBN 9781498738750 (e-book : alk. paper)
Subjects: LCSH: Titanium-aluminum alloys. | Joints (Engineering)
Classifi cation: LCC TN693.T5 S537 2017 | DDC 669/.7322--dc23
LC record available at https://lccn.loc.gov/2017008753
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Preface
γ-TiAl alloys are a novel class of advanced structural materials which
enlarge the possible choices of materials for high temperature applications,
especially when the weight reduction of the components is critical
for structural applications. The development and processing of high
temperature materials is crucial to technological advances in engineering
areas where materials have to meet extreme demands. γ-TiAl alloys have
a series of properties that make them attractive to the aerospace and
automotive industries and are being used to produce components for the
new generation of aircraft engines and automotive turbochargers.
The joining of components is an essential part of a man-made product
manufacturing. The joining processes often contribute significantly to
the cost of the final product and to the production difficulties. γ-TiAl
alloys can be successfully joined by processes such as friction welding,
brazing, diffusion bonding and transient liquid phase bonding. These
processes do not require the melting of the base material and therefore the
joints do not present high residual stress, so that the formation of some
deleterious intermetallics can be prevented. However, very demanding
bonding conditions are needed to produce a sound interface with the
desired mechanical properties. Even when the bulk materials remain at
temperatures significantly below their melting point (such as in soldering,
brazing and diffusion bonding), the required processing temperatures
often induce phase transformations, structural modifications and localised
stresses that impair the properties of the joints.
The joining of γ-TiAl alloys, either to themselves or to dissimilar
materials, requires the application of new strategies in order to obtain good
quality joints in appropriate processing conditions. This book describes
the current state of knowledge regarding the bonding of these advanced
materials, with emphasis on the techniques used by the authors, who for
more than a decade, have undertaken research into the joining of these
materials by solid-state diffusion bonding and brazing, together with teams
from the Universities of Coimbra and Minho.
This book has been organised into eight chapters—three introductory
chapters covering the applications, structure and conventional processes
for joining γ-TiAl alloys, followed by five chapters focusing on the use
vi Joining Technology of -TiAl Alloys
of reactive multilayers to bond γ-TiAl alloys to themselves and to other
materials. This book is intended for students, materials scientists, engineers,
and technicians who desire to familiarise themselves with the joining of
γ-TiAl alloys and with the new developments in this field.
Sónia Simões
Filomena Viana
Manuel F. Vieira
Acknowledgements
This book is the result of a collaborative research work and fruitful
discussions with many colleagues working in the field of joining of
advanced materials. Though it would be impossible to thank all those
who have directly or indirectly contributed to this project, a few specific
references will be made to the following contributors.
We would like to acknowledge the invaluable cooperation of the team
from the University of Coimbra (CEMUC), Prof. Dr. Maria Teresa Vieira
and Dr. Ana Sofia Ramos, in all aspects related to the reactive multilayer
systems and to the team from the University of Minho, Dr. Ana Maria Pinto
and Dr. Aníbal Guedes, in the brazing of γ-TiAl alloys. The authors are also
very grateful to Dr. Mustafa Koçak for his scientific and technical support
and to the facilities provided at the Helmholtz-Zentrum Geesthacht.
We would like to acknowledge the financial support of the Fundação
para a Ciência e Tecnologia-FCT and the Faculty of Engineering, University
of Porto-FEUP.
Finally, we would like to thank our colleagues, co-workers and students
at the Department of Metallurgical and Materials Engineering, University
of Porto, for their encouragement and suggestions.

Contents
Preface v
Acknowledgements vii
List of Abbreviations xiii
List of Figures xv
List of Tables xxiii
1. γ-TiAl Alloys 1
1.1 Introduction 1
1.2 Structure of γ-TiAl Alloys 2
1.3 Properties of γ-TiAl Alloys 6
1.4 Processing of γ-TiAl Alloys 8
1.5 Concluding Remarks 11
1.6 References 12
2. Joining of γ-TiAl Alloys 15
2.1 Introduction 15
2.2 Fusion Welding 16
2.3 Friction Welding 20
2.4 Brazing 23
2.5 Concluding Remarks 27
2.6 References 28
3. Diffusion Bonding of γ-TiAl Alloys 30
3.1 Introduction 30
3.2 Diffusion Bonding 31
3.2.1 Diffusion Bonding Parameters 32
3.2.2 Interdiffusion in γ-TiAl Intermetallics 34
3.3 Diffusion Bonding of γ-TiAl Alloys 35
3.3.1 Diffusion Bonding of γ-TiAl Alloys using Interlayers 44
3.4 Concluding Remarks 48
3.5 References 49